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Shimano UN55 Bottom Bracket

Item #: BB257F01
USD$14.99 SAVE 36% USD$23.39 msrp
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Shimano UN55 Bottom Bracket

Shimano UN55 Bottom Bracket

High quality Shimano sealed bottom bracket (square taper). Extra strong Aluminum (not plastic) non drive cup. Please choose width and spindle length.

  • English Threaded
4.7 / 5.0
81 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Stars
62
16
2
1
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The Classic "55" - affordable fit
used this bb to revamp an early Fuji Gran Tourer. Despite my wanting to use the adjustable factory bb, the oem spindle was pitted beyond use. Good replacement spindles in the correct width in fairly short supply. This UN55 with it's many spindle lengths was a quick & inexpensive fix to get the Gran Tourer road worthy again.

PROS: Enhances Pedaling Efficiency, Durable, Lightweight, Easy To Install
September 9, 2013
Location:
10kLakes
Good for the price
Installed on my SSCX commuter, more solid feel than an unsealed bb. Would recommend for the price, definitely better than the un26 option.

PROS: Easy To Install, Enhances Pedaling Efficiency
August 25, 2015
Location:
Colorado Springs, CO
Easy to replace bottom bracket
I was glad to be able to replace the bottom bracket on my own. Easy instructions.

PROS: Enhances Pedaling Efficiency, Easy To Install
August 5, 2014
Location:
Olathe, KS
K.I.S.S. Bang for the buck
I use this bb on a cross build to get proper chainline after removing holotech bb going from double to triple.

PROS: Easy To Install, Durable

BEST USES: Road Biking, Mountain Biking
February 13, 2014
Location:
Vestal, ny
Meets my expectations
I replaced a Shimano BB-LP27 that had 450+ miles on it. This UN55 was a perfect upgrade and perfect fit. Just be carful when trying to thread the aluminum cup. The threads are very fine, it will test you patience. The correct tools for the job are a must. I also purchased them for a great price from Jenson.

PROS: Lightweight, Easy To Install, Enhances Pedaling Efficiency, Durable
April 2, 2014
Location:
Kingston MA.
So good, I had to buy another one.
I had bought one of these for my road bike, and had such good luck with it, when my Kona Lanai started clunking, I got one for it. I didn't realize how bad my bottom bracket was, until I changed it. Wow, what a difference it made, the bike rides so much better now.

PROS: Durable, Enhances Pedaling Efficiency, Easy To Install

CONS: None
July 31, 2014
Location:
Kingman, Az.
works fine.
Never had a problem with the old bracket until it wore out after 8 years of riding. This is a replacement and it works as it should. Make sure you get the right length bottom bracket when replacing the worn out unit. Also pay attention to direction things are threaded. It's not the same on both sides.

PROS: Easy To Install

CONS: Req Special Instal Tools
May 29, 2013
Location:
Houston, TX
Great product, replaces vintage BB's.
Replace that worn out original BB with one of these easy to install and use Shimano BB's. Many sizes to choose from, even Italian threaded. These are concentric, so remember to add extra when measuring for the drive side of your crankset. The late, great Sheldon Brown covers this in his writings.

PROS: Easy To Install, Durable

CONS: Not Enough Sizeslengths
April 8, 2014
Location:
Fresno, Central California
Execellent Easy to Install
I used this to replace the cheap factory FSA that was a heavy steal consturciton, yet quickly (under 500 miles) developed a grating sound while cranking hard up hills. Though I am a heavier rider at 210lbs and am riding a low end bike that's just one step up from buying one off the shelf at Walmart. Installation was easy, only had to do a minor adjustment on the high and low stops of the front derailer as the offset was slightly different on the drivetrain side from the FSA bracket. Pedalling feels smoother after around 200 miles on the new bottom bracket than it ever did on this bike before. Happy so far with this product.

PROS: Easy To Install
August 14, 2014
Location:
Moberly, MO
Good fix to worn cup and spindle bb
I've used this bottom bracket a couple times to replace pitted and rusted spindles. Very easy installation and reliable. Although, I do like my RaceFace external bearing bb a little better.

PROS: Easy To Install, Enhances Pedaling Efficiency
August 7, 2014
Location:
Cape Cod ,MA

Q & A

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Browse 7 questions Browse 7 questions and 13 answers
What tool would I need to install this?
Dan on Jun 26, 2016
BEST ANSWER: Park Tool makes two tools that fit this bottom bracket, The BBT-2 and the BBT-22
Is the left bolt left hand threaded or are they both right handed?
craig on Jul 28, 2017
BEST ANSWER: One is right, the other is left hand threatened. I do not remember which, but would assume the right dide is right, and the left is left. Be sure of the over all length (width). If not correctly sized you will have difficulties w/the front derailleur adjustment.
I'm replacing a LP27E 113/73. It has '1.37 x 24' on it. Will this work as a replacement and still be able to accommodate the E-type front derailleur? If so, will I need to add spacers or do something else to ensure everything fits correctly and the chain line is not affected?
A shopper on Apr 22, 2017
BEST ANSWER: Yes, the UN55 BB will work. Just make sure that you order 113 x 73. 113mm is the spindle length and 73mm is the bottom bracket shell width. 1.37 x 24 refers to the thread diameter & thread pitch. 1.37 x 24 is known as English thread.

You will use your E-type derailleur mount instead of the drive-side spacer - chain line should be good.
I have Panasonic bike from 1982 and it is 68mm x 124.7mm do I go down to the 122.5mm or up to the 127mm on the bottom bracket?
Jayhawker on Apr 12, 2016
BEST ANSWER: I would go with the larger 127mm size axle, because the smaller than original size axle may cause your largest chain ring to touch the frame. Also note you may need to adjust your derailleur since your chain rings will be moved slightly outward,
Installing vintage Suntour Superbe Pro cranks on (very) old Specialized ...will 68 X 107 work with the Superbe Pro (NJS) track cranks?
A shopper on Apr 19, 2017
BEST ANSWER: Spec is 109mm, but 107mm is pretty close. You'll probably be fine.
What is a good front Derailleur Match for the 127mm version of this BB? I bought this from Jensen, but my Shimano 105 front can't fully reach the large Chain ring now.
A shopper on Mar 13, 2017
BEST ANSWER: You may have to put a spacer on the drive side to move the chainring out to where it was previously.
What bolts are needed for attaching crank?
PHIL on Jul 27, 2016
BEST ANSWER: Basic hex head 8mm x 1mm x16mm bolts are included in the UN55 package. Fancier hex socket bolts with rubber seals are included with some of the Shimano crank sets.

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Free Shipping Offer

Get free Standard Shipping with your $50 purchase today! Just choose Standard Shipping during checkout.

Please note this offer is only available to physical shipping addresses in the 48 continental United States (no PO Boxes), and oversize charges still apply on some heavy/large items.